To: TigerPaw who wrote (1180 ) 8/13/2000 11:07:55 PM From: TigerPaw Read Replies (1) | Respond to of 69300 Eyes Assume man had no eyes and we needed to form them. What do we need from random chance? DNA changes would have to occur to effect nervous, skeletal, muscular, vascular and endocrine systems - all at once, to form. 2 bony orbits in skull to house the eyes with holes (foramina) for nerves and vessels. Globe - sclera, choroids, and retina with its rods and cones and specialized visual chemicals, vitreous body, lens, suspensory ligament and ciliary muscle, iris (with its control nerves) cornea, aqueous humor, canal of schlemm, and internal circulation of blood. Muscles with nerves to control eye movements. Optic nerves with crossover pathways. Visual cortex in the brain with the ability to fuse the images and interpret the millions of nerve signals each second and connect with the rest of consciousness in the brain. Vestibular mechanism and also the life saving spinal cord reflexes. All features must be perfectly integrated and balanced with all other systems. Plus we need eyebrows, eyelids, eyelashes, conjunctive, tear glands, tear ducts, pigment for the iris and genes to control the color (Drosophila has 15 genes to control eye color). If everything in not just right, it would be worse than no eyes at all. (Try wearing your neighbor's glasses!) Ugg, there are plenty of web sites to show that all vision forms from simple photodetectors - such as the back of your arm which will feel "hotter" on the side facing the sun - to the greatest of eyes (which are not human) are all still available as examples in living animals. Each improvement is a slight change, but conveys a distinct advantage in the appropriate circumstance. Eyes have evolved multiple times. TP